(1) Field of the Invention
This invention relates to improvements in vehicle safety systems, and in particular to a system for use in a vehicle such as a snowmobile, which is effective to prevent or terminate operation of the engine upon malfunction of the control elements of the engine.
(2) Description of the Prior Art
Because of the adverse climatic conditions in which they frequently operate, small recreational vehicles such as snowmobiles can sometimes be subject to serious malfunction of the engine control elements. For example in snowmobiles the engine speed is usually controlled by a throttle lever mounted on the handlebar and connected to a carburetor control valve or piston through a bowden cable. The quantity of fuel/air mixture delivered to the engine, and consequently the engine speed, is governed by the carburetor valve or piston in response to movements of the throttle lever, spring means being provided to restore the carburetor valve or piston to an idle position when the lever is released. In certain climatic conditions such systems can fail, due to freezing of the carburetor valve or piston, the cable, or the throttle lever itself, resulting in a stuck throttle condition. When this condition arises, the engine may continue to operate at high speed even after the throttle lever has been released. To counteract this problem, present day snowmobiles commonly are equipped with a key and with a "kill switch" which is located close to the throttle lever and distinguished by color coding. Both of these devices can be activated in a stuck throttle situation to short circuit the engine ignition system and thus terminate operation of the engine.
However, while both these devices can be of assistance, operators often do not read the owner's manual and do not become familiar with the operation of these devices. Thus in a crisis situation, the operator sometimes panics and fails to activate the kill switch or the key.
Also of concern is the situation in which the engine has a stuck throttle condition when the operator attempts to start the engine. Snow-mobiles normally have automatic centrifugally operated clutches in a belt transmission between the engine and the driving track. Such clutches respond solely to engine speed, being disengaged at idle speed, but automatically forming a driving connection between the engine and the track as the engine speed increases. If the snowmobile engine is started when the throttle is stuck wide open, the engine speed will within a few seconds reach an RPM which will automatically engage the clutch and set the vehicle in motion. Thus the vehicle can start to move very quickly immediately upon starting of the engine. Although this situation can be easily prevented by checking for the free movement of the throttle control system before starting the vehicle and most present day snowmobiles do not require that the throttle be applied to start the vehicle, operators sometimes disregard these instructions and when a crisis occurs panic and fail to activate the kill switch or the key.
It is the object of this invention to alleviate problems arising through malfunction of the control elements of vehicle engines particularly, although not exclusively, in snowmobiles and to minimize the need for active response by the operator to correct the situation.